Implement miette library for enhanced CLI error reporting

[Copilot]

This PR refactors the CLI error handling to use the miette library for rich, user-friendly error reporting. The changes provide better error messages with diagnostic codes, helpful suggestions, and improved formatting.

Changes Made

Dependencies

• Added miette dependency with fancy feature for enhanced error formatting

Error Type Improvements

• Enhanced ConfigError with miette diagnostic attributes and helpful suggestions
• Enhanced FormatError with diagnostic codes and context-aware help messages
• Added diagnostic codes for better error categorization (e.g., roughly::config::invalid, roughly::format::syntax)

CLI Error Reporting

• Added report_diagnostic_error() function for consistent miette error display
• Updated configuration error handling to use miette reporting
• Updated format error handling to use miette reporting
• Maintained backward compatibility with existing error types

Testing

• Added comprehensive tests to verify miette integration
• All existing tests continue to pass
• New tests validate error formatting and diagnostic capabilities

Before vs After

Before:

error: invalid config file
failed to read config

After:

roughly::config::invalid

  × Invalid config file format
  ╰─▶ TOML parse error at line 4, column 17
        |
      4 | [invalid_section
        |                 ^
      invalid table header
      expected `.`, `]`
      
  help: Check the TOML syntax in your roughly.toml file

Key Benefits

• Rich Error Context: Errors now include source code context and precise location information
• Helpful Suggestions: Each error type provides actionable help messages
• Diagnostic Codes: Structured error codes for better tooling integration
• Improved UX: Better visual formatting with colors and clear hierarchy
• Backward Compatibility: All existing functionality preserved

The implementation focuses on configuration and format errors as these are the most common user-facing errors, while maintaining the existing error handling patterns for other parts of the codebase.

Fixes #44.

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[felix-andreas-copilot]

@copilot please use miette in cli::check instead of custom formatting logic

[Copilot]

@copilot please use miette in cli::check instead of custom formatting logic

I've successfully replaced the custom formatting logic in cli::check with miette-based error reporting. The changes include:

• Added a new CheckDiagnostic enum with miette attributes for rich error display
• Created a helper function to convert LSP diagnostics to miette format
• Replaced ~70 lines of custom formatting code with miette's built-in capabilities
• Added comprehensive tests to validate the new functionality

The check command now provides much better error display with proper source code context, highlighting, and consistent formatting. All tests are passing.

Commit: c9e9f9c